I don't know that it would be a good idea even if it did work.
It is likely that the type of memory used in the IPOD is not suitable for intensive memory use. Even USB pen drives really aren't up to the job on a long term basis. If you think about it, the memory in USB drives isn't really meant to be repeatedly read / written / over-written and Ipods and the like will be no better.
PC Advisor has some weird fixation about Readyboost judging by the number of times it gets a mention in the magazine. It will make a noticeable difference if you have around 512MB RAM and a very slight difference with 1GB RAM. Anything over that it's a complete waste of effort.